1. Field of the Invention
This invention relates to the field of handheld computers and display illumination. In particular, the present invention relates to an efficient personal digital assistant display illumination system and method that is easily adaptable to integrate touchpad capability.
2. Related Art
Electronic systems and circuits have made a significant contribution towards the advancement of modern society and are utilized in a number of applications to achieve advantageous results. Numerous electronic technologies such as digital computers, calculators, audio devices, video equipment, and telephone systems facilitate increased productivity and cost reductions in analyzing and communicating data, ideas and trends in most areas of business, science, education and entertainment. Electronic systems designed to produce these results often include electronic displays, such as a portable handheld computer display screen. Traditional display screen illumination techniques in a handheld computer usually result in uneven and inefficient illuminating of a presentation on the display screen.
Typically, the primary function of a display screen is to provide a clear and readily viewable presentation to a user. One of the most important factors affecting a users ability to easily perceive the shapes or images of a presentation is sufficient illumination of the display screen. Ambient light is often insufficient to provide adequate illumination of a display screen and a display screen usually includes lighting provisions such as a backlight. Effective distribution of light from a light source to the display screen significantly impacts the clarity of a display screen presentation.
Traditional computer display illumination techniques often provide light from a single source onto a light pipe and rely on the light pipe to function as a distribution medium. While a light pipe does provide some beneficial distribution characteristics, light emanating from a single source usually does not get distributed evenly through a light pipe and some areas of a display screen often appear significantly darker than other areas. It is usually more appealing to have an evenly illuminated display screen. Evenly illuminated display screens usually provide a more pleasant viewing experience without significant contrasts. Traditional illumination attempts sometimes rely on a relatively large light source that consumes considerable energy and while it may increase illumination to darker areas of a display screen it usually does not solve contrast problems because some areas of the display screen still typically appear very bright compared to others. FIG. 1 shows an illumination display pattern of a prior art display screen in which areas 111, 112 and 121 are darker than 107 which is darker than 105. Light waves from light source 131 that travel some distance (e.g., 195) to the light pipe 145 often miss the light pipe and are absorbed by the device body 150.
As the components required to build a computer system have reduced in size, new categories of computer systems have emerged. One of the new categories of computer systems is the hand held or xe2x80x9cpalmtopxe2x80x9d computer system. A palmtop computer system is a computer that is small enough to be held in the hand of a user and is often xe2x80x9cpalm-sized.xe2x80x9d Most palmtop computer systems are used as Personal Digital Assistants (PDAs) to implement various Personal Information Management (PIM) applications such as an address book, a daily organizer, and electronic notepads, to name a few. Even though palmtop computer systems are very small, they typically provide diverse functionality and their capabilities are constantly increasing. Display capabilities of handheld computers are becoming increasingly important and due to the relatively small size of the display in a handheld computer it is important for the presentation to be clear and well illuminated.
The relatively small size of a typical handheld computer increases the difficulty of accomplishing a number of operations, including illuminating a display. Typically, the compactness of a handheld computer limits the size of a light source and it is important to effectively utilize the limited light emissions. A light pipe in a handheld computer is usually so thin that significant portions of the light generated by a light source miss the light pipe and are absorbed by relatively non reflective materials that form other portions of the hand held computer.
Efficient distribution of light to a display usually facilitates significant improvements in display presentations. Typically, the more efficiently light is delivered to a display the clearer the presentation of shapes and images and the more pleasurable the viewing experience is for a user. Efficient lighting of a display also permits a smaller light source and a smaller light source consumes less of the limited energy supply most portable handheld computers rely on to supply power. Displays that are easy to view and smaller components (such as a light source or battery) facilitate palmtop computers size reductions allowing greater portability and ease of use.
What is required is a system and method that facilitates efficient and relatively even distribution of illumination throughout a display. The system and method should also facilitate clearer presentation of images, size reductions and conservation of limited power resources in handhled computers.
The present invention system and method facilitates efficient and relatively even distribution of illumination throughout a display. The system and method also facilitates clearer presentation of images, size reductions and conservation of limited power resources in handheld computers. In one embodiment of the present invention, a display illumination distribution system includes a light pipe, a lens, a wave guide array and a light source. The light source provides light waves that are directed along the wave guide array to the lens which direct the light waves into a light pipe included in a display module. The routing of light through the wave guide array confines the light waves to a wave guide and reduces the number of light waves that miss the light pipe. In one embodiment of the present invention the interior walls of each wave guide comprise a highly reflective material that reflects light waves down the length of the wave guide with minimal light loss due to absorption. In one embodiment of the present invention, the display illumination distribution system and method directs visible light waves through a wave guide array to multiple points along the edge of a light pipe included in the display module and provides more effective distribution of light into the light pipe.